LZDoom

LZDoom is a of the GZDoom source port centered around lower-end computers by drfrag. LZDoom follows GZDoom's feature set and has a few enhancements of its own. It employs an based renderer, as GZDoom moved away to  as a hardware requirement. LZDoom targets users still running with OpenGL 2.1 compatible graphics cards but who want to stay in touch with the latest in GZDoom development.

History
LZDoom was originally started as another legacy oriented build of GZDoom, built around version 3.3. Eventually, another one of drfrag's ports, GZDoom Vintage was merged into the existing codebase to create one new unified port under the same name. The first version of LZDoom as result of this merging was version 3.82, released on July 19, 2019, seven days after the last Vintage release.

Future developments
Starting from LZDoom 4.5.0, the port will move to a more recent GZDoom build, dropping the OpenGL 2.1 renderer altogether in favor of the SoftPoly II renderer, a full 3D polygonal renderer that runs on the CPU on a hardware accelerated backend.

Features

 * All features from latest version of mainline GZDoom (ACS, ZScript, ZMusic etc)
 * All ZDoom features
 * Rudimentary support for Doom Legacy (To run existing Legacy mods like Ni'mRoD - IXNAY on the HOMBRE)
 * Support for the DEHEXTRA standard
 * OpenGL 2.1 based renderer (OpenGL 3.3+ recommended):
 * Full 3D floors (including slopes)
 * Reflective floors
 * Dynamic lights, brightmaps, glowing flats, custom
 * ' and '-style skyboxes in addition to regular ZDoom skyboxes
 * Optional High-quality (HQnX) rescaling filters for graphics, sprites and textures
 * MD2, MD3 and DMD model support
 * 4 player splitscreen (LZDoom-exclusive)
 * Options to switch between 9 and  rendering for software (Worldsim, backend)
 * Several fixes to mods to maintain compatibility

Merged features from QZDoom
The QZDoom codebase enhancements partially also found their way into LZDoom, courtesy of Magnus Norddahl (dpJudas) and Rachael Alexanderson (Eruanna). These include:
 * Polygonal, 3-point perspective truecolor software renderer (“Softpoly”)
 * Truecolor support for the classic 2-point renderer
 * Vulkan renderer backend
 * Proper windowed mode support (i.e. you can freely resize the game window)
 * Correct ZDoom software light mode for the hardware renderer
 * High resolution correct version of the software fuzz, for both software and hardware renderers